FR2564148A1 - FUEL PUMP WITH TWO FLOORS - Google Patents

Abstract

THE INVENTION RELATES TO A TWO-STAGE FUEL PUMP. THIS PUMP INCLUDES A CRANKCASE 10 INCLUDING AN INLET 14 AND AN OUTLET 94 FOR THE FUEL, A FIRST STAGE 18 HAVING AN INTAKE OPENING INTO THE ADMISSION CHAMBER 12 AND AN OUTLET OPENING IN AN INTERMEDIATE CHAMBER 40 SHAPED IN THE CRANKCASE 10, A SECOND STAGE 20 INCLUDING AN INLET OPENING INTO THE said INTERMEDIATE CHAMBER 40 AND AN OUTLET, MEANS 70, 74, 88 CONNECTING THE OUTLET OF THE SECOND STAGE 20 OF THE PUMP TO THE FUEL OUTLET 94, AND MEANS 50 SERVING TO MAINTAIN THE PRESSURE IN THE INTERMEDIATE BEDROOM 40 BELOW A PREDETERMINED MAXIMUM VALUE. APPLICATION IN PARTICULAR TO AIRCRAFT PISTON ENGINES.

Description

The present invention relates to fuel pumps

  intended for aircraft or aircraft engines and more particularly a pump of this type comprising two stages

pumping.

  Previously known fuel pumps

  intended for use in aircraft engines with

  typically use a single-stage fuel pump to send fuel to the engine. Although being

  at low altitude, these fuel pumps

  the engine with insufficient fuel

  at higher altitudes, because of the strong de-

  inlet pressure and as a result of vapor formation of the fuel. The strong entrance depression reduces

  the efficiency of the pump, while a vap

  these two phenomena, which contribute to the fact that the pump de-

  delivers a reduced amount of fuel.

  In order to send a sufficient quantity of

  motor at high altitudes, for example to

  titudes exceeding 5400 meters, known aircraft engines

  previously had an electric surge pump

  in tandem with the normal fuel pump. When activated at high altitudes,

  these electric supercharging pumps send a quantity

  additional fuel to the engine in order to

  re the engine's fuel requirements.

  However, these electric boost pumps, known previously, have the disadvantage of being expensive and also increase the weight of the aircraft. In

  in addition to these known supercharging electric pumps

  have a relatively short life span when operating during time intervals

  prolonged, which requires maintenance and / or replacement

  frequent and expensive charging of the booster pump.

  The present invention provides a fuel pump

  two-stage solution that solves all the disadvantages

  previously derived from aircraft fuel systems, previously known. Briefly, the fuel pump according to the present invention comprises a housing having a fuel inlet opening into a cylindrical intake chamber. Fuel intake is tangential

  relative to the intake chamber so that the fuel

  rant swirls when entering the room of admission.

  mission. The heavier fuel is directed, under the action of centrifugal force, towards the outer periphery of the intake chamber, while the lighter vapors

  fuel flow to the center of the chamber

  ridges. These fuel vapors are evacuated from the chamber.

  intake by means of a source of depression.

  Both stages of the pump are mounted so that they can rotate inside the housing and are driven

  in rotation through a motive power

  this on the engine of the plane. The first stage inlet is connected to the vortex chamber and its outlet is connected to an intermediate chamber within the pump housing. Similarly, the admission of

  second stage of the pump is connected to the intermediate chamber.

  and its output is connected via a fuel control valve to the fuel outlet of

the pump.

  A bypass passage of the fluid is formed at

  the inside of the fuel pump housing between the

  intermediate chamber and the admission chamber. A valve

  the pressure is actively connected to the center point of this bypass

  the fuel pressure in the intermediate chamber de-

  passes a predetermined pressure, equal for example to 24.5.

  104 Pa. Therefore, if a recirculation is performed

  part of the fuel from the

  medial back to the admission chamber or to the

6 4 1 48

  swirl chamber, the pressure inside the chamber

  the intermediate pressure is kept equal to the preset pressure.

  completed. The fuel control valve responds to a state of the engine, such as for example the output pressure of a turbojet to variably direct a portion of the fuel delivered by the second stage into the intake chamber or the vortex chamber or at the outlet of the pump. So, when the request of the

  engine increases, the fuel control valve

  rant directs a larger part of the fuel

  second stage of the pump towards the pump outlet and a smaller portion of the fuel is

  recirculated back to the inlet of the pump. inverted

  When the fuel demand decreases, the fuel control valve

  fuel to the tower chamber.

  and a smaller portion of the fuel in

the output of the pump.

  An expansion valve is also connected, from

  from a hydraulic point of view, in series between the

  fuel and the vortex chamber. This expansion valve is normally kept in the open state under

  the effect of the fuel pressure so that the fuel

  penetrant in the expansion valve enters the chamber.

  admission. Conversely, during a state of

  When the engine is idling, the expansion valve closes substantially, causing the fuel to

  at the fuel outlet so as to maintain the fuel

  fuel to the engine during a running condition.

  in slow motion. A manually controlled mixing valve

  fuel is connected in series with the fuel outlet

  to allow the pilot to modify manual-

  the fuel mixture sent to the engine as it

the desire.

  Other features and advantages of the pre-

  invention will emerge from the description given below.

  after referring to the accompanying drawings, in which: - Figure 1 is a block diagram showing a preferred embodiment of the fuel pump according to the present invention; FIG. 2 is a longitudinal sectional view of the preferred embodiment of the invention; FIG. 3 is an end view of the form

  preferred embodiment of the invention considered essential.

  along the direction corresponding to lines 3-3 in Figure 2;

  FIG. 4 is a sectional view taken substantially

  line 4-4 in Figure 3, but

  90 clockwise; and

  FIG. 5 is a view considered essential

  along line 5-5 of Figure 2.

  Here we will give a detailed description

  of a preferred embodiment of the invention.

  Referring first to Figures 1 and 2, there is shown a preferred embodiment of the fuel pump of the present invention, which includes a housing 10 defining a cylindrical inlet or a cylindrical vortex chamber 12. intake 14 of the fuel opens into the intake chamber 12 and its axis is tangential to the cylinder of the intake chamber 12. Therefore the fuel entering the inlet 14 of the housing to end in the inlet chamber 12 performs a swirling motion inside the chamber 12 so that the intake chamber 12 forms a

whirlpool chamber.

  The swirling action of the fuel has the

  the interior of the intake chamber 12 causes the denser liquid fuel to move towards the periphery

  outside the chamber 12 under the action of the

  trifuge, while the lighter fuel vapors are directed towards the central portion of the intake chamber 12. These fuel vapors are discharged by a vacuum source or vacuum source (not shown) via a hydraulic connection 16 located at the ex-

  upper end of the intake chamber 12.

  A first pumping stage 18 and a second coaxial pumping stage 20 are rotatably mounted inside.

  a bore 22 formed in the casing 10, which extends

  radially outwardly from the axis of the intake chamber 12. Preferably the pump stages 18 and 20 are constituted by volumetric type finned pumps, the first stage 18 being of a size

  greater than that of the second stage 20.

  As best seen in Figures 2 and 3, the stages 18 and 20 of the pump are separated from each other by a spacer 24 which is attached to the two stages 18 and 20 of the pump such that so that these stages 18 and 20and the spacer device 24 turn

  the concert. A drive shaft 16 is attached to one end

  mite 28 of the second stage 20 of the pump while its other end 30 has a square hole 32 which opens into an opening 34 located in the housing 10 of the pump. A

  energy intake (not shown) on the motor is accu-

  mechanically folded, near the square hole 32, the shaft 26 so as to rotate the stages 18 and 20 of the pump. Conventional hydraulic seals 36 are also provided between the casing 10 of the pump and the shaft 26 so as to eliminate any leakage of the fuel

out of the pump.

  Referring now to FIG. 2, it is seen that a sleeve 38 is disposed in the bore 22 of the housing around the spacer 24 and between the stages

  18 and 20 of the pump. This sleeve 38 has a circular channel

  conference in its outer periphery and which

  form an intermediate annular chamber 40 between

  18 and 20 of the pump. A bypass passage 42 for the fuel is provided in the casing 10 of the pump and

  has an end 44 opening into the internal chamber

  40, while its other end 46 opens into the intake chamber 12. A valve seat 48 is formed at a midpoint of the bypass passage 42, for a

  reason that will be described later.

  A pressure-sensitive valve assembly 50 is housed in a valve housing 52 and is secured to the pump housing by screws 54. The valve assembly 50 includes a valve member 56 which cooperates with the seat valve 48 formed in the bypass passage 42 of

  opening and closing the passage of

42.

  The bypass valve assembly 50 preferably has an anode 58, which is pressure sensitive.

  prevailing in the intermediate chamber 40. When the

  in the intermediate chamber 40 exceeds a predetermined value, for example 35.4.10 Pa, the anérolde 58 contracts by retracting thereby the valve member 56 from its closed position shown in Figure 2, and opening of this makes the bypass passage 42. A rod

  threaded 60 and a nut 62 allow adjustment of the pressure

  opening pressure of the bypass valve assembly 50.

  Referring now in particular to FIG. 1, it can be seen that the admission of the first stage 18 is

  connected by a hydraulic passage 64 to the chamber of admission

  12 while its output is connected by a

  66 to the intermediate chamber 40. Similarly, the ad-

  mission in the second stage 20 is connected by a hydraulic passage 68 to the intermediate chamber 40, while

  the output of the second stage 20 opens into a hyphenated passage

  The hydraulic passages 64, 66, 68, 70 are all preferably made in the housing 20.

pump.

  Referring now to FIGS. 1, 2 and 4, it will be seen that the passage 70 from the outlet of the second stage 20 is connected, hydraulically, to the lower chamber 72 of a fuel control valve 74.

  valve 74 includes an upper chamber 76, while a first

  fice 78 connects rooms 72 and 76.

  Referring now in particular to the

  1 and 2, it can be seen that the upper chamber 76 of the fuel control valve 74 is connected in a hydraulic connection formed by a hydraulic passage 80,

  has a chamber 82 (Figure 2)) located in a set of val-

  of relaxation 84. In all the conditions of

  the engine, except in the case of idling, the fuel pressure in the chamber

  82 keeps the expansion valve 84 in an open position.

  te, so that the fuel flowing in the passage 80 enters the chamber 82 and the passage 86 (FIG.

  1) and is returned to admission chamber 12. The function

  of the expansion valve subsequently described

  in more detail. Conversely, an additional passage

  88 connects, in a hydraulic connection, the lower chamber 72 of the fuel control valve 74 to a fuel outlet chamber 90 (FIG. 2) provided in FIG.

  the casing 10 of the pump. The fuel outlet chamber 90

  rant is then connected in a hydraulic connection via a fuel mixing valve 92 &

the outlet 94 of the fuel.

  Referring & water to my figures! and 4, we see that the fuel mixing valve has a rod

  96 fuel control system, which is mounted so that it can

  To slide inside a hole 98 formed in a housing 100 provided for the valve 74. The fuel control rod 96 comprises a rare tronconiue 102 which is coaxial with and adjacent to the orifice 7G so that

  the axial displacement of the fuel control rod 96

  FIG. 4 shows a variable limit on the orifice 78 as shown by a dashed line. As a result, when the fuel control valve 96 is moved to a raised position, a larger portion of the fuel exiting the second stage enters the passage 88 (Figure 1) and the outlet chamber 90 (Figure 2). Conversely, when the stem of

  fuel control 96 is brought to a lower position

  which opens port 78, a larger part

  fuel aunt escaping from the exit of the second floor

  is returned to admission chamber 12 through

  the chamber 82 of the expansion valve, which is re-

  linked to the fuel outlet 94 via the

chamber 90 (Figure 2).

  Referring now in particular to FIG. 4, it can be seen that the position of the fuel control rod 96 is controlled by an aneroid 104 which is

  attached to the rod 87. This anode 104 is housed in a chamber

  106 formed in the valve housing 100. A hy

  hydraulic -108 opens in room 106 and is connected,

  hydraulic connection, to an indi-

  as the engine speed. Such a pressure source may be constituted for example by a tap on the pressure outlet of a turbojet engine. Consequently, when the pressure inside the chamber 106 increases, the anerotus 104 contracts, which causes the sending of a larger quantity of the fuel to the outlet of the chamber.

  94. When the pressure inside the chamber

  decreases, indicating a reduction in the speed

  of the engine, the anérolde 104 expands and consequently

  by recirculation, a larger part of the car-

  112. A threaded rod and a nut 112 allow adjustment of the initial position of the control rod 96 and consequently of the

  amount of fuel recirculation.

  Referring now in particular to the

  gures 2 and 5, it can be seen that the fuel mixture valve 92

  allows the driver to enrich or impoverish manually

  the fuel supply sent to the engine. The valve

  fuel control 92 includes a body 114 which is

  rotating on the housing 10 of the pump, so that the

  pilot has access to one end 116. A piercing 118 is

  ge in the opposite end of the body 114, which opens into the outlet chamber 90, while a slot 120 arranged

  in the body 114 is aligned with the bore 118 and connects

  therefore the latter has the fuel outlet 94.

  As best seen in Figure 5, a rotation

  body 114 leads to an increase or decrease in

  duction of the alignment zone between the slot 120 and the

  fuel outlet 94, so as to allow a limitation of

  variable flow of fuel delivered by the outlet chamber 90 and sent to the outlet 94 of the pump. As shown in FIG. 2, a stop device 122 fixed to the body 114 limits, in association with a locking pin 124 fixed to the casing 10 of the pump, the rotation angle of the body 114 of the control valve. fuel between a full fuel enrichment position

  and a position of complete depletion of fuel.

  Referring now to Figure 2, we see

  that the expansion valve device 84 has a diaph-

  128 applies to an expansion valve member 130. For all engine operating conditions other than idle operation, the fuel pressure in the pressure valve chamber 82 acting on the diaphragm 128 maintains the 130 of the valve

  in its open position shown in FIG.

  2. In this open position, essentially the whole

  ble of the amount of fuel entering the chamber

  82 of the expansion valve is returned to the room of admission

  12 through the passage 86 (Figure 1).

  Conversely, during the operating state of the engine at idle, the pressure in the chamber 82 of the expansion valve is insufficient to maintain the member 130 of the expansion valve in its open position, so that this member 130 is move to the left by

  compared to its position shown in FIG.

  the organ 130 of the expansion valve essentially closes

  the hydraulic passage 86 (Figure 1) and creates a counter-

  pressure in the passage 80 of the fuel. This counter-pressure

  The coupling pushes the fuel out of the second stage outlet through the passage 88 and towards the fuel outlet 94, through the outlet chamber 90 and the air-fuel mixture valve 92. A screw 134 and a spring 136

  allow the adjustment of the opening pressure

the expansion valve.

  During operation, at relative altitudes -

  The output signal delivered by the first stage of the pump is lower than the pressure of the bypass valve assembly 50 so that the bypass valve assembly 50 opens and allows some of the fuel

  issued by the intermediate chamber 40 to be returned to

  culation or be returned to the intake chamber 12. The remaining fuel passes through the second stage 20 of the pump

  and the fuel mixing valve 74 which sends a quantity

  variable fuel consumption to the engine according to the

  these required operation of the latter. The remaining fuel passing through the fuel control valve 74

  is returned or recirculated to the

admission number 112.

  When the engine altitude increases, beyond

  Typically 3400/6000 meters, the pressure inside the chamber 40 decreases due to the strong inlet depression, as well as due to the formation of

  fuel vapor. This reduction of pressure to the in-

  interior of the intermediate chamber 40 has the effect that the

  Bypass valve 50 appears to move toward its closed position, which limits or even closes off bypass passage 42. Bypass 42 is further restricted or closed, a larger amount of fuel is sent from the first stage 18 of the pump towards the second stage 20 of the pump, which maintains a sufficient supply of fuel to the engine at higher altitudes, for example

  altitudes of 7600 meters, without the need for

  use electric boost pumps, previously known. From the above, we can see that this

  invention provides a fuel pump assembly that is suitable for

  especially for a piston engine and maintains a fuel supply

  at engine, at high altitudes. On the basis of the pre-

  description,] those skilled in the art who can

  will be able to make many changes without

depart from the scope of the invention.

Claims (11)

  A fuel pump, characterized in that it comprises: - a housing (10) having a fuel inlet (14) and a fuel outlet (94), said fuel inlet   feedthrough into a fuel inlet chamber (12)   rant formed in said housing, - a first stage (18) of the pump having an inlet opening into said inlet chamber (12) and an outlet opening into an intermediate chamber (40) formed in said housing (10), - a second stage (20) of the pump having an inlet opening into said intermediate chamber (40), and an outlet; - means (70, 88) for hydraulically connecting the outlet of said second stage (20) of the said fuel outlet (94); - means (50) for maintaining the pressure within said intermediate chamber (40) below a value predetermined maximum.   2. Fuel pump according to claim 1,   characterized in that said means (50) for maintaining the   pressure include means for connecting hydraulically   lique said intermediate chamber (40) to said chamber of ad-   mission (12) when the pressure prevailing in said chamber   intermediate exceeds said predetermined value.   3. Fuel pump according to claim 1,   characterized in that said means (50) for maintaining the pressure include: -   a hydraulic bypass passage (42) extending between   said intermediate chamber (40) and said admission chamber   a valve seat (48) forming an orifice connected in series with said bypass passage (42) and mounted at a central point thereof, - a valve member (56) movable between a closed position wherein said valve member closes said orifice and an open position, wherein said valve member (20) is spaced from said orifice and opens the orifice, and - pressure sensitive means (58) for displacing variable said valve member (56) between said open and closed positions.   4. Fuel pump according to claim 1,   characterized in that it is used in an engine comprising a state representative of the speed of the engine, characterized in that it further comprises means (74) hydraulically connected to said output of the second stage (1) of the pump and responsive to said engine state for hydraulically connecting the output of said second stage (20) of the pump at said intake chamber (12).   5. Invention according to claim 4, characterized in that said variable hydraulic connection means (74) comprise: - a hydraulic passage (88) connecting hydraulically   the output of said second stage (20) to said chamber of admission sion (12),   an orifice (78) connected in series with said hydraulic passage   and means (96, 104) responsive to said engine condition for   to limit in a variable manner said orifice.   6. Fuel pump according to claim 5,   characterized in that said engine state is a hydraulic pressure and said means (96) providing a limitation   variable include a tapered valve that can be moved   axially in said orifice (78) and an air bellows   stiff (104) connected to said conical valve and responsive to said auditory state of the engine.   7. Fuel pump according to claim 5,   characterized in that said inlet chamber (12) has essentially a cylindrical shape, means (14) for introducing the fuel tangentially inside the   said chamber and hydraulically connected means (16)   than at one end of said chamber to evacuate the steam.   8. Fuel pump according to claim 5,   characterized in that it comprises an expansion valve (84) having a hydraulically connected chamber in series with said orifice (78) and with said inlet chamber (12), said expansion valve (84) being movable in an open position, in which the flow of the leakage flow entering said expansion chamber (82) enters said inlet chamber (12), and a closed position, wherein said expansion valve (94) stops flow of fluid from said expansion valve chamber into said admission chamber.   9. Fuel pump according to claim 3,   characterized in that it comprises a sensitive anolyte (58)   at the pressure and attached to said valve member (56).   Fuel pump according to claim 1,   characterized in that each stage (18, 20) of the   carries a volumetric fin pump.   Fuel pump according to claim 10, characterized in that said stages (18, 20) of the pump are coaxial.